Ionized-gas beam-shifting tschebyscheff array antenna



Jan. 2, 1962 1.. B. BROWN ETAL 3,015,822

IONIZED-GAS BEAM-SHIFTING TSCHEBYSCHEFF ARRAY ANTENNA 2 Sheets-Sheet 1 Filed March 25, 1960 INVENTOR5 ELWIN w. SEELEY LAWRENCE B. BR W WILLIAM R. JONES Jan. 2, 1962 B. BROWN ETAL 3,015,322

IONIZED-GAS BEAM-SHIFTING TSCHEBYSCHEFF ARRAY ANTENNA Filed March 23, 1960 2 Sheets-Sheet 2 co m m N N CUR RENT 44 4 FIG. 2

FIG. 4

m NW c 3') INVENTORS ELWlN W.SEELEY LAWRENCE B. BROWN WILLIAM .R. JONES United States Pati IONIZED-GAS BEAM-SHIFTING TSCHEBYSCHEF ARRAYANTENNA Lawrence B. Brown, Anaheim, Calif., William R. Jones, Hillsdale, N.J., and Elwin W. Seeley, Riverside, Califl, assignors to the United States .of' America represented by the Secretary of theNavy Filed Mar.23, 1960, Ser. No. 17,234 3 Claims. (Cl. 343-771) .(Granted under Title 35, U.S. Code (1952) sec. 2 66) l The invention herein described may be manufactured I and usedby or for the Government o'f'the' United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

, The invention relates to antenna phase shifters and more particularly to a device for sweeping a microwave beam through small angles at high scan rates by varying the permittivity of a gas within an antenna waveguide section.

Previous sweeping antennas required construction using waveguide fed slots or dipoles in which the guide wavelength was changed by mechanically moving one side of the waveguide or by moving material inside the waveguide. Such mechanical units were difficult to manufacture, assemble, and adjust; also they were subject to mechanical wear, and the rate at which a beam could be swept was rather low. In the present invention sweep rates up to 100,000 cycles per second are possible without moving the antenna array. The present device sweeps a microwave beam through small angles at high scan rates by varying the permittivityof an ionizable gas within a particular waveguide section by changing a D.C. current passing through the gas thereby varying the ionization thereof. The efiect of the present device is to vary the wave length of the waveguide and hence vary the squint angle of the antenna by electronic means rather than mechanical means Therefore, the antenna may be smaller in size, lighter in weight, less expensive, and easier to adjust than previous mechanical units, and also not subject to wear.

It is an object of the invention, therefore, to provide a novel means for antenna phase shifting without the need for moving mechanical parts.

It is another object of the invention to provide a sweep ing beam antenna using an ionized gas as a variable dielectric.

Another object of the invention is to provide a novel by electronic means and is not subject to mechanical wear.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood byreference to the following detailed description when considered in connection with the accompanying'drawings wherein: FIGURE 1 is a perspective view of a preferred embodiment of the beam-switching array antenna of the present invention; I

FIGURE 2 is top planar view of the array antenna of FIGURE 1; V i

FIGURE 3 is across-sectional view taken along line 33 of FIGURE 2; v

FIGURE 4 is a bottom planar view of the antenna of FIGURE 1; 7

FIGURE 5 is a cross-section taken alongline 5'+-5 of FIGURE 2.

Referring now to the drawings, like numerals refer to like parts in each of the figures.

The beam switching array antenna'is composedofan.

r 3,015,822 I. Patented Jan. 2 1962 X-band flange 10 having a section 12 or X-band waveguide. mounted thereon and a quartz window13 mounted in the bottom thereof. A section 14 ofre'ctangular coaxial waveguide is mounted on the X-band waveguide section 12, perpendicular to a broad side thereof, such thatthe center conductor 16 of the rectangular coaxial waveguide 14 is one-fourth wavelength (it/4) from the closed end 18 of'X-band waveguide section 1 2. One end of center conductor "16 protrudes intowaveg'uide section 12 approximately to the center thereof. The R.F. input is applied at the open end ofwaveguide 12',-as arrow 45 indicates, while the R.F. output emanates throu ghwindow 22, as shown by arrow 40. The variable current source 44,. supplies a varying'cur rent flow betweenfelectrode16, to which 'itis connected by lead 42 to the terminal 30', and'theout er shell-I4-Which is led to groundbylcad fll Ground? lead 43 completes the ei'rcuit The broad sur face- 20 of rectangular coaxial waveguide section 14, which faces away from the X-bandflange 10, has. a Tschebyscheff antenna array cut therein. The array slots 22 are small windows of quartz or the like. Central conductor 16 is centrally supported within waveguide section 14 by supports 24 of dielectric material such as Teflon, for example.

The closed end 26 of the rectangular coaxial waveguide section 14 has a pass-through capacitor, such as disclosed in U.S. Patent No. 2,456,803 to Harold: A. Wheeler, mounted therein which is connected to the end of central coaxial conductor 16 at 28. The other end of the pass-through capacitor serves as an ionizing current feed terminal 30. By means of terminal 30 a D.C. potential can be applied between center conductor 16 and the outside conductor of waveguide 14.

The interior of the antenna assembly is completely sealed ofi from the outside atmos'phereby means of passages 32 and 34 which are used for evacuating the applied between ,the inner and outer conductors of coaxial waveguide 14 will ionize the gas within the section.

While previous antennas have varied the guide wavelength by moving the side of the waveguide or by moving some material within the waveguide to result in vary.

ing the squint angle, the present invention does not move a dielectric within the waveguide or move a portion thereof. The present devicecperates by varying the permittivity of a stationary dielectricwithin the waveguide, i.e. the inert ionizable gas wi-thinthe waveguide which acts as the dielectric. The permittivity of the dielectric is a function of the number of ionized gas molecules per unit volume.

squint angle of the array. 'The D.C. current may be changed at rates up 'to approximately 100,000 cycles per 7 second.

Since the present invention varies the squint angle by Y electronic rather than mechanical means it has a decided While the embodimentdescribed herein isfor operating at X-band frequencies, the principle of operation is general andv may be applied to antenna designs for any frequency above the-gas plasma oscillation frequency. a Obviously many modifications and variations of the Therefore, the guide wavelength may be varied by changing the D.C. current through the gas a which changes the number of ions-and thus change the present invention are possible in the light of the above teachings. It is thereforeto be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described, What is claimed is: 1

1. A beam shifting array antenna adapted to uniformly and quickly shift the ionization level of a gaseous medium operatively associated therewithin comprising a section of coaxial waveguide defined by an outer. conductor of rectangular cross-sectionhaving a pair of relatively wide faces and a pair of relatively narrow faces and an inner conductor coaxially disposed relative to said outer conductor, means closing the ends of said waveguide section to define an enclosed chamber therewithimsaid inner conductor being spaced from said wide faces by a distance that is small compared to its length, a rare ionizable gas filling said enclosed chamber, anarray of slots formed in the Tschebyscheff pattern on one of said wide faces, said slots having sealed windows thereacross, input means for applying R.F. input energy to one end of said waveguide, a source of, R.F. energy connected to said input means, a sourcelofvarying current for rapidly changing the ionization levelof said gas whereby its permittivity,

and thus the wavelength of the Waveguide, is varied, and

means connecting said current source across said outer conductor and said inner conductor.

2. An antenna as in claim 1 wherein said windows are composed of quartz.

3. An antenna as in claim 2 wherein said waveguide includes means for supplying the gaseous medium there- Witbin and wherein said rare gas is neon.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Microwave Transmission Circuits, by George L. Ragan, McGraw-Hill Book Co., New York, 1948. 

